MySQL 从存储过程中检索 last_insert_id

Posted 2023-05-09

【中文标题】MySQL 从存储过程中检索 last_insert_id

【英文标题】：MySQL retrieve last_insert_id from stored procedure

【发布时间】：2020-05-20 09:40:46

【问题描述】：

我正在使用 NodeJS 和 mysql 通过 post_tag 保存帖子及其标签：

DROP TABLE IF EXISTS post_tag;
DROP TABLE IF EXISTS post;
DROP TABLE IF EXISTS tag;
DROP PROCEDURE IF EXISTS select_all_posts;
DROP PROCEDURE IF EXISTS insert_post;

CREATE TABLE post (
  id INT NOT NULL AUTO_INCREMENT,
  title VARCHAR(45) NULL,
  body TEXT NULL,
  PRIMARY KEY (id));

CREATE TABLE tag (
  id INT NOT NULL AUTO_INCREMENT,
  tag VARCHAR(45) NULL,
  PRIMARY KEY (id));

CREATE TABLE post_tag (
  post_id INT NOT NULL,
  tag_id INT NOT NULL,
  PRIMARY KEY (post_id, tag_id),
  INDEX fk_post_tag_tag1_idx (tag_id ASC),
  INDEX fk_post_tag_post_idx (post_id ASC),
  CONSTRAINT fk_post_tag_post
    FOREIGN KEY (post_id)
    REFERENCES post (id),
  CONSTRAINT fk_post_tag_tag1
    FOREIGN KEY (tag_id)
    REFERENCES tag (id));

INSERT INTO post (id, title, body) VALUES (1, 'post 1', "Post body");
INSERT INTO post (id, title, body) VALUES (2, 'post 2', "Post body");
INSERT INTO tag (id, tag) VALUES (1, 'tag 1');
INSERT INTO tag (id, tag) VALUES (2, 'tag 2');
INSERT INTO post_tag (post_id, tag_id) VALUES (1, 1);
INSERT INTO post_tag (post_id, tag_id) VALUES (1, 2);
INSERT INTO post_tag (post_id, tag_id) VALUES (2, 1);

我创建了一个存储过程来插入新帖子：

-- Stored procedure to insert post and tags
DELIMITER $$
CREATE PROCEDURE insert_post(
  IN title VARCHAR(45),
  IN body TEXT
)
BEGIN
  INSERT INTO post (title, body) VALUES (title, body);
END $$
DELIMITER ;

所以在节点中我可以做到：

var mysql = require("mysql2");
var connection = mysql.createConnection(
  host: "127.0.0.1",
  user: "test_database",
  password: "test_database",
  database: "test_database",
);

connection.connect();

const postTitle = JSON.stringify("Post 3");
const postBody = JSON.stringify("This is post 3 body");
const insertPostQuery = "CALL insert_post(" + postTitle + "," + postBody + " )";

connection.query(insertPostQuery, (error, results) => 
  console.log(JSON.stringify(results, null, 4));
);

connection.end();

这会返回：

    "fieldCount": 0,
    "affectedRows": 1,
    "insertId": 0,
    "info": "",
    "serverStatus": 2,
    "warningStatus": 0

现在我想从存储过程中检索最后插入的id，所以我修改我的存储过程添加一个OUT last_inserted_id INT参数，然后在INSERT之后赋值：

-- Stored procedure to insert post and tags
DELIMITER $$
CREATE PROCEDURE insert_post(
  IN title VARCHAR(45),
  IN body TEXT,
  OUT last_inserted_id INT
)
BEGIN
  INSERT INTO post (title, body) VALUES (title, body);
  SET last_inserted_id = LAST_INSERT_ID();
END $$
DELIMITER ;

但是在节点中执行查询时，这将返回 undefined 而不是带有 last_inserted_id 值的 json。

我做错了什么？

【问题讨论】：

在我看来，将标量值作为函数返回的代码更符合逻辑...

嗨@Akina，谢谢。你能举个例子吗？只是一个草图，以了解您的意思。

您的 out 参数是第三个参数，但您使用两个参数调用该过程。将原始值直接注入 SQL 字符串也感觉不对。

感谢@ÁlvaroGonzález;儿子 ejemplos lo más sencillos posible。 Quiero ver si tengo opciones de volver a MySQL o si tengo que quedarme con los ORM。

【参考方案1】：

你能举个例子吗？

CREATE FUNCTION insert_post_fn(
  in_title VARCHAR(45),
  in_body TEXT
)
RETURNS BIGINT
MODIFIES SQL DATA
BEGIN
  INSERT INTO post (title, body) VALUES (in_title, in_body);
  RETURN LAST_INSERT_ID();
END

使用方法：

SELECT insert_post_fn('Post title', 'This is post body') AS `LAST_INSERT_ID`;

---

CREATE PROCEDURE insert_post_proc(
  IN in_title VARCHAR(45),
  IN in_body TEXT,
  OUT out_id BIGINT
)
BEGIN
  INSERT INTO post (title, body) VALUES (in_title, in_body);
  SET out_id = LAST_INSERT_ID();
END

使用方法：

CALL insert_post_proc('Post title', 'This is post body', @id);
SELECT @id AS `LAST_INSERT_ID`;
-- PS. Variable name used is random
-- PPS. Both statements must be executed 
--      in the same connection and without reconnect

---

CREATE PROCEDURE insert_post_proc(
  IN in_title VARCHAR(45),
  IN in_body TEXT
)
BEGIN
  INSERT INTO post (title, body) VALUES (in_title, in_body);
  SELECT LAST_INSERT_ID() AS `LAST_INSERT_ID`;
END

使用方法：

CALL insert_post_proc('Post title', 'This is post body');

---

fiddle